This invention relates to an information playback apparatus for playing back information recorded on a recording medium.
A technique for magneto-optically recording information onto a disk and playing back the recorded information has conventionally been developed, and as the amount of information handled increases, increase of the disk capacity is demanded. Here, since it is demanded to decrease the size itself of the magneto-optical disk taking facility in handling and so forth into consideration, the density of information recorded on the magneto-optical disk has been and is being increased. One of available techniques for increasing the density of information recorded on the magneto-optical disk is to decrease the track width.
This method, however, gives rise to a problem that, as the distance between adjacent tracks, that is, the track pitch, decreases, it becomes liable to detect an address signal recorded on an adjacent track as crosstalk.
In particular, because of the fact that the track pitch is small, a pickup may possibly read an address different from a correct address signal, resulting in failure in detection of a correct address. If a correct address cannot be detected, information cannot be recorded or played back at the correct position of the magneto-optical disk.
Further, if a synchronizing signal included in an address recorded in an adjacent track is detected, then an address decoding circuit provided in a disk drive apparatus which drives the magneto-optical disk operates inadvertently. Consequently, there is a problem that the disk drive apparatus may operate in a similar manner as in a case wherein an error occurs with reading out of an address. Such problems as described above significantly appear particularly where the disk drive apparatus which plays back information recorded on the magneto-optical disk suffers from disturbance and scanning of the pickup is rendered less accurate thereby.
It is an object of the present invention to provide an information playback apparatus which can play back information with a high degree of accuracy.
According to an aspect of the present invention, there is provided an information playback apparatus which plays back a land address and a groove address, from a recording medium on which a land and a groove are formed adjacently each other such that the land address is recorded on the land and the groove address is recorded at a position of the groove displaced from the land address in a direction along which the land and the groove extend, including:
information readout means for reading out information recorded on the recording medium, by scanning the land or the groove;
detection means for detecting the land address or the groove address included in the information read out by the information readout means to produce a detection signal and output the detection signal;
masking means for masking, the detection signal produced while the information readout means passes the land adjacent to an area in which the groove address is recorded in case that the information readout means scans the land, and the detection signal produced while the information readout means passes the groove adjacent to an area in which the land address is recorded in case that the information readout means scans the groove, within the detection signal supplied from the detection means to produce a synchronism detection signal; and
decoding means for decoding the information read out by the information readout means in response to the synchronism detection signal produced by the masking means to produce the land address or the groove address.
With the information playback apparatus, a synchronism detection signal can be produced while a detection signal produced through crosstalk is eliminated with certainty by the masking means. Consequently, the land address and the groove address can be played back with a high degree of accuracy. Accordingly, the accuracy in information playback can be raised.
Preferably, the information playback apparatus further includes error detection means for detecting an error portion included in the land address or the groove address produced by the decoding means, and producing and outputting a notification signal representing that the land address or the groove address is correct data in case that the error portion is not detected, and wherein the masking means includes masking signal production means for producing a masking signal having a predetermined logic level in a predetermined period for which the detection signal is masked by counting the period of time after a point of time at which the notification signal is supplied from the error detection means, and operation means for performing two-input logical operation between the detection signal and the masking signal to produce the synchronism detection signal.
With the information playback apparatus, an influence of crosstalk upon reading out of an address can be eliminated using a simple configuration and with certainty. Consequently, the accuracy in information playback can be raised without increasing the circuit scale or the cost significantly.
The above and other objects, features and advantages of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings in which like parts or elements denoted by like reference symbols.